1. Field of the Invention
The present invention is concerned with a dental care material and a method for producing the material. It is especially concerned with a material suited for orthodontic appliances and dental implantation.
2. Description of Related Art
Among the materials used in a human mouth are wire and brackets for orthodontics and dental implantation. Depending on the use, plastics, ceramics, and stainless steel, etc., have traditionally been the most commonly used materials. In some cases utilization has been made of Ti--Ni system alloys, Ni--Cr system alloys, and Fe--Ni--Cr system alloys. However, there is an increasing number of patients who suffer from metal allergies, caused by a particular metal touching and irritating the skin and causing roughness or inflammation. Among such metal allergies are skin allergies caused by earrings, necklaces, and other accessories, and allergies caused in the mouth by the metals used in dental care. No one metal is the cause of the allergies, and individuals differ in regard to which types of metal cause allergies. More serious than allergies is the carcinogenic nature of such metals as Ni and Cr. The use of Ni--Cr system alloys on a living human body is even prohibited in some countries.
With each of the dental care materials mentioned above there are problems, such as mechanical characteristics, production costs, the elution of the material into the body, compatibility with living tissues, etc. For example, plastics may break due to lack of strength; ceramics are too expensive; stainless steel results in too much elution, which, like the alloys mentioned above, may cause problems such as allergies and cancer.
In addition, from the molding material perspective, brackets and dental implantation have traditionally been produced by the casting method and mechanical processing. With the casting method, the problem of breakage during use often occurs due to defective casting, especially due to the formation of casting pockets. In addition, the creation of complicated shapes is difficult in casting due to the problem of running liquid. For example, the shape of the surface of a bracket to be bonded to teeth, or the shape of the screw component for an implant material, is too complicated to be produced exactly as designed. Thus, in the case of the bracket, there is insufficient bonding strength. In regard to the dental implantation, after implanting an implant material, the screw may loosen causing breakage of the upper structure or a mismatching bite, resulting in difficulty in chewing food.
On the other hand, when the process involves mechanical processing, such as cutting, there is difficulty in processing materials with a high level of hardness, especially titanium materials that have poor machine processability, resulting in products with poor precision. For example, the screw component of a dental implantation must be mechanically processed because it cannot be produced by casting. Poor precision in the screw component can allow the entrance and spread of infectious agents to the screw component, which is screwed inside the mandibula. These infectious agents include Escherichia coli, Candida, Pseudomonas aeruginosa, staphylococcus, and aureus, which cause halitosis and susceptibility to gum diseases.